Playing Groovy Tunes on PPSSPP version 1.7.1, with the graphics API being Vulkan.

The anime plays perfectly (it suffers from the fact PSP'S natural resolution is low, though)
"Overmaster" is perfectly playable, with correct video switching. (the user Aidolu said the song failed to play, so had to make a separate section for this song)
Othe songs: Yet to test, please wait. So far "Marionette no Kokoro" is perfectly playable, with correct video switching.

However, the character "♪" still cannot be rendered (refer to GabrieliosP's post for details).